Dry rotary joint



Sept. 3, 1968 -r CARY ET AL 3,400,357

DRY ROTARY JOINT Filed Dec. 9, 1966 2 Sheets-Sheet 1 INVENTORS JOHN T. CARY CHARLES R. LOCKE RICHARD F. SCHARF 3 BY 50 a MARTIN F. AHRENS 4 mwms Sept. 3, 1968 J. CARY ET AL 3,400,357

DRY ROTARY JOINT Filed Dec. 9, 1966 2 Sheets-Sheet 2 JOHN T. CARY INVENTORS CHARLES R. LOCKE RICHARD F. SCHARF 8| MARTIN F. AHRENS BY Mam, fidwb, WW

United States Patent 3,400,357 DRY ROTARY JOINT John T. Cary, Markham, Charles R. Locke, Western Springs, Richard F. Scharf, Chicago, and Martin F. Ahrens, Palos Park, lllL, assignors to Continental Can Company Inc., New York, N.Y., a corporation of New York Filed Dec. 9, 1966, Ser. No. 600,461 17 Claims. (Cl. 339-8) This invention relates in general to new and useful improvements in electrical connections, and more particularly to a low and substantially constant resistance rotary conductor to be used to transfer electrical energy involving high levels of current with a minimum and substantially constant voltage drop and consequent power dissipation.

The primary consideration of a rotary joint is low and constant resistance. If the resistance is high, an excessive amount of power will be lost in the rotary joint, causing heating, arcing, pitting, and other adverse phenomena which contribute to rapid deterioration of the rotary element. In addition, these same factors typically result in a constantly changing resistance, which causes great difficulties in controlling the energy delivered to the load. The joints and workpiece are the two primary elements in the secondary, high current circuit. Since the resistance heating is determined by the square of the current, the importance of the resistance of the rotary joint becomes obvious.

A further qualification is that the rotary unit, when utilized in the welding of side seams of can bodies, must be able to be contained within a small space, such as that realizable within a horn structure limited to the internal size of the can body to be welded.

In accordance with this invention, there has been provided a dry silver-graphite sliding contact joint which provides the necessary rotary connection and has a low and constant resistance throughout the life thereof and at the same time is capable of transferring electrical energy involving high levels of current while being sufiiciently small to be confined within the horn structure of a can body maker.

Another object of this invention is to provide a silvergraphite sliding contact rotary joint which is of a construction to assure a constant contact and at the same time may be readily cooled by the circulation of a coolant through the internal construction thereof.

A further object of this invention is to provide a combination rotary joint and roller electrode holder wherein the roller electrode, while being replaceable on the rotary joint, is cooled utilizing the same coolant which is circulated through the rotary joint.

A still further feature of the invention is to provide a dry silver-graphite sliding contact rotary joint wherein the brushes include a combination of different ratios silvergraphite compositions to ensure the desired filming of the components contacted by the brushes while still maintaining high current capability.

With the above and other objects in view that will hereinafter appear, the nature of the invention will be more clearly understood by reference to the following detailed description, the appended claims and the several views illustrated in the accompanying drawings:

In the drawings:

FIGURE 1 is a side elevational view of a welding horn, with parts broken away and shows mounted therein a combined rotary joint and roller electrode construction in accordance with this invention.

FIGURE 2 is an enlarged transverse vertical sectional view taken along line 2-2 of FIGURE 1 and shows the specific internal construction of the rotary joint and the mounting of the roller electrode.

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FIGURE 3 is an enlarged longitudinal sectional view taken along the line 3--3 of FIGURE 2 and shows further the construction of the rotary joint.

FIGURE 4 is an enlarged fragmentary longitudinal vertical sectional view taken along the line 44 of FIG- URE 2 and shows specifically the coolant arrangement for the roller electrode and the spring arrangement for the brushes of the rotary joint.

FIGURE 5 is an enlarged fragmentary transverse sectional view taken along the line 5-5 of FIGURE 4 and shows further the coolant supply arrangement for the roller electrode.

Referring now to the drawings in detail, it will be seen that there is illustrated in FIGURE 1 a portion of a welding horn which is referred to by the numeral 10. The welding horn 10 is of a configuration to receive tubular members which are to have the side seams thereof formed by welding. Although particular reference will be made to the welding horn 10 as being part of a can body maker, it is to be understood that the welding horn could be utilized in the formation of other tubular members. The welding horn 10 has a recess 11 formed therein in which there is seated a combined rotary joint and roller electrode assembly which is referred to in general by the numeral 12.

The rotary joint portion of the assembly 12 includes a tubular body which is generally referred to by the numeral 13. The tubular body 13 has two sleeve portions 14 which are integrally connected together by a central hub 15. The hub 15 includes a central web which extends transversely of the hub intermediate the sleeve portions 14.

Each of the sleeve portions 14 is provided adjacent its axially outer end with an internal groove 17. A similar groove 18 is formed on the inner surface of each sleeve portion 14 along the central portion thereof. As a result of the grooves 17 and 18, each sleeve portion 14 has a pair of internal contact surfaces 20 which are generally ring shaped.

A conical pin 21 projects into and is generally coextensive with each of the sleeve portions 14. Each conical pin 21 has an outer contact surface 22 which generally opposes the contact surfaces 20' of the respective sleeve portion 14.

Referring now to FIGURE 3 in particular, it will be seen that each sleeve portion 14 is provided in the inner surface thereof with a plurality of axially elongated, circumferentialy spaced, radial grooves or slots 23. Each of the grooves or slots 23 has positioned therein a separating blade 24, the outline of which is best shown in FIGURE 2. It is to be noted that the separating blades 24 are spaced radially from the contact surfaces 22 of the pins 21.

Between each pin 21 and the respective sleeve portion 14 is a plurality of brushes 25. Each brush 25 is segmental in transverse section and wedge shape in longitudinal section as shown in FIGURES 3 and 2, respectively. The outer surface of each brush 25 is of a radius of curvature corresponding to the radius of curvature of the contact surfaces 20, and the inner surface of each brush 25 is of a conical surface configuration corresponding to the conical surface configuration of the contact surface 22 of the pin 21. Thus, a full mating contact between the brushes 25 and the contact surfaces 20 and 22 of the sleeve portion 14 and the pin 21, respectively, is assured.

In order to assure constant and even contact of the brushes 25 with the sleeve portion 14 and the pins 21 notwithstanding the gradual wearing of the brushes, there is provided a spring assembly which is generally referred to by the numeral 2 6. The spring assembly 26 is carried by the transverse web .16 and engages the opposed ends of the brushes 25 and resiliently urges them apart. In

order to provide clearance for the spring assembly 26, the opposed ends of the pins 21 are provided with enlarged bores 27.

The spring asembly 26 is insulated from the body 13 and includes a central bushing 28 which is formed of a suitable insulating material. n opposite sides of the transverse web 16 and in abutting engagement with the bushing 28 are insulated washers or discs 29. On opposite sides of the transverse web 16 outwardly of the insulating washers 29 there are springs 30. This assembly is clamped together by a bolt 31 and a nut 32 with the bolt passing through the springs 30, the washers 29 and the bushing 28. If desired, the bolt 31 may be provided with a lock washer 33.

Referring now to FIGURE 4 in particular, it will be seen that each spring 30 is formed of a central hub 34 having radiating therefrom a plurality of spring fingers 35 which are offset from the plane of the hub 34 in the manner best shown in FIGURE 2. It is to be noted that there is one spring finger 35 for each of the brushes 25 of the set of brushes with which the spring 30 is associated, and each spring finger 35 is centered relative to its respective brush 25.

At this time it is pointed out that the pins 21 and the body 13 are preferably formed of coin silver or copper, with the preferred copper being tellurium copper. On the other hand, the brushes 25 are of a silver-graphite composition. It has been found that a 93-7 silver-graphite composition provides the best results. It has also been found that if one of the brushes of each set of the brushes is of a greater graphite composition, it encourages the formation of a friction-resistant film on the contacting surfaces 20 and 22 so as to hold to a minimum the friction between the surfaces and prevent galling thereof while maintaining the high current capability of the joint.

It is to be noted that the pins 21 are provided with outer mounting portions 35 which include shoulders 36. The right-hand pin in FIGURE 2 is suitably seated in a seat 37 formed directly in the horn 10. The mounting portion 35 of the left-hand pin of FIGURE 2 is seated in a seat 38 formed in a mounting block 40 which is formed separate from the horn 10, but is suitably secured therein in a fixed position. Thus, the pins 21 are restricted as to their spacing.

It is to be noted that each of the sleeve portions 14 is rotatably journalled in a bearing 41. The horn is provided with a seat 42 for receiving the bearing 41 of the right-hand sleeve portion while the block 40 is provided with a seat 43 for receiving the bearing of the lefthand sleeve portion. It is to be noted that suitable insulation 44 and 45 is positioned in the seats 42 and 43 so as to prevent electrical conduction through the bearings 41.

It is also pointed out at this time that the exterior of the body 13 is sealed relative to the horn 10 and the block 40 adjacent the opposite ends of the sleeve portions 14. Around the end of each sleeve portion 14 there is a ring 46 which is formed of a suitable firm plastic material. Associate with each ring 46 is a resilient sealing ring 47. The rings 46 and 47 are seated in annular grooves 48 and 49 formed in the horn 10 and the block 40, respectively.

It is to be noted that the hub has an annular projection 50 which is offset from the transverse web 16. A roller electrode 51 is removably seated on the hub 15 in abutting engagement with the projection 50. The roller electrode 51 is retained in place by means of a clamping nut 52 which is threaded onto an externally threaded portion 53 of the hub 15.

At this time it is pointed out that the roller electrode 5.1 is of a two-piece construction and includes a main part 54 which is of a C-shaped cross section. The second part of the roller electrode 51 is in the form of a ring having an annular projection 56 which projects into and reinforces the main part 54. A pair of annular gaskets 57 and 58 seal the ring 55 relative to the main part 54. As a result, the roller electrode 51 has a coolant passage 60 formed therein. The coolant passage 60 is, however, not continuous but has closely spaced end portions separated by a web 61 formed integral with the main part 54, as is shown in FIGURE 4. Thus, circulation of a coolant through the roller electrode 51 is assured.

In order to assure circulation of coolant through the roller electrode 51, there is formed in the hub 15 to the left of the transverse web 16 an internal annular groove 62. A generally Z-shaped passage 63 extends from the annular groove through the hub 15 and terminates in a port 64 which opens out through that face of the projection 50 against which the roller electrode 51 is seated, as is best shown in FIGURE 5. The main part 54 of the roller electrode is provided with an inlet port 65 which is aligned with the port 64. An annular sealing ring 66 seals the roller electrode 51 relative to the projection 50 so as to prevent the escape of fluid passing through the ports 64 and 65.

The hub 15 is provided with a second internal annular groove 67 to the right of the transverse web 16. A passage 68 extends generally radially outwardly from the groove 67 within the hub 15 in general and the projection 50 in particular and terminates in a port 69. The port 69 is aligned with a second port 70 in the roller electrode. The port 70 is disposed at the end of the passage 60 remote from the port 65. An annular sealing ring 71 seals the ports 69 and 70.

It is to be noted that each of the pins 21 is provided with a coolant port 72. One of the coolant ports 72 will be an inlet port and the other will be an outlet port. The born 10 will be provided with suitable coolant passages (not shown) through which coolant will fiow to the rotary joint 12 and return therefrom.

Each of the pins 21 is provided with a plurality of radial passages 73 extending from the port 72 to the exterior of the respective pin 21 at the outer ends of the brushes 25. Coolant flow is between the brushes 25 in the space 74 between the separating blades 24 and the pins 21. It is to be noted that the spaces 74 open into the annular grooves 62 and 67. Thus, a single coolant flow through the rotary joint not only cools the components of the rotary joint, but also the roller electrode 51. It will be readily apparent that the sealing rings 47 prevent the flow of coolant around the exterior of the body 13.

As is best illustrated in FIGURE 2, the born 10 is of a dimension to receive a tubular body 75 which is to be provided with a welded seam. During the welding operation, a second roller electrode 76 cooperates with the roller electrode 51 to form the welded seam.

It is to be noted that the rotary joint has been carefully designed to maximize contact between rotary and stationary elements. It is for this reason that a multiplicity of contact segments are provided. In addition, water is provided around the contact segments or brushes as well as within the roller electrode for cooling. The silvergraphite brushes encourage the formation of a water film between contact elements to provide cooling there, but also to decrease resistance, ensure current distribution through all possible surface area, and remove particulate material which may be eroded from one or the other of the contacting elements. If this material is not removed, it may wedge between the surfaces, cause arcing or nonuniform current density or otherwise contribute to rapid deterioration of the conductors.

It is to be understood that the rotary joint is designed to fit within a very small area, such as the horn 10 when the horn 10 has a diameter of two and inches. At the same time, the rotary joint must conduct an extremely high current, a current on the order of 5,000 amperes. In the particular rotary joint which has been successfully utilized, the conducting area is on the order of two square inches thereby giving a typical current density of 2,500 amperes per square inch.

It is to be noted that the brushes are mounted so as to be of the floating type. Thus, the brushes can automatically adjust to compensate for wear and thereby provide longer life between replacement of brushes.

Although only a preferred embodiment of the invention has been specifically illustrated and described herein, it is to be understood that minor variations may be made in the rotary joint without departing from the spirit and scope of the invention as defined by the appended claims.

We claim:

1. A rotary conductor for transferring electrical energy involving high levels of current, said conductor comprising a tubular body, conical pins projecting into said body from opposite ends thereof in axial alignment with each other and said body, a set of segmental brushes arranged circumferentially around each conical pin, and means resiliently urging said brushes into electrical energy transferring contacting relation with said pins and said body.

2. The rotary conductor of claim 1 wherein said body has a transverse web disposed intermediate said pins, and said resilient means being carried by said transverse web.

3. The rotary conductor of claim 1 wherein said resilient means are in the form of a spring element for each set of brushes, and each spring element having a separate finger engaging each brush of the respective set of brushes to individually urge each brush into place.

4. The rotary conductor of claim '1 wherein said body has a transverse web disposed intermediate said pins, said resilient means being carried by said transverse web, said resilient means are in the form of a spring element for each set of brushes, and each spring element having a separate finger engaging each brush of the respective set of brushes to individually urge each brush into place.

5. The rotary conductor of claim 1 wherein said brushes are formed of a silver-graphite composition.

6. The rotary conductor of claim 1 wherein said brushes are formed of a 93% silver-7% graphite composition.

7. The rotary conductor of claim 1 wherein said brushes are formed of a silver-graphite composition, the ratio of silver to graphite in a majority of said brushes being high, and at least one brush of each set of brushes having a low silver to graphite ratio to form a controlled film on said pins and said body.

8. The rotary conductor of claim 1 wherein said brushes are formed of a silver-graphite composition, and said body and said pins are formed of copper.

9. The rotary conductor of claim 1 wherein said brushes are circumferentially spaced by means of axially extending spacers, and means are provided for circulating a coolant within said body between said brushes.

10. The rotary conductor of claim 1 wherein said brushes are circumferentially spaced by means of axially extending spacers carried by said body, and said pins have means for circulating a coolant within said body between said brushes.

11. The rotary conductor of claim 1 wherein said body has directly mounted thereon a roller electrode.

12. The rotary conductor of claim 1 wherein said body has directly mounted thereon a roller electrode, said electrode being hollow and said brushes being circumferentially spaced, and means for directing coolant through one set of brushes, around through said electrode and out through the other set of said brushes.

13. The rotary conductor of claim 1 wherein said body is rotatably journalled within a support, and said pins are fixedly carried by said support.

14. The rotary conductor of claim 1 wherein said conductor is part of a welding unit for welding seams in tubular members and is mounted within a horn-type support for tubular members, said pins being fixedly carried by said support and bearings rotatably journalling said body within said support, and a roller electrode carried by said body.

15. The rotary conductor of claim 1 wherein the current density through said rotary conductor is on the order of 2500 amperes per square inch.

16. The rotary conductor of claim 1 wherein said brushes are formed of a silver-graphite composition, and said body and said pins are formed of a metal from the group consisting of coin silver and copper.

17. The rotary conductor of claim 1 wherein said brushes are formed of a silver-graphite composition, and said body and said pins are formed of coin silver.

References Cited UNITED STATES PATENTS 2,063,718 12/1936 Berndt 339273 XR 2,558,041 6/1951 Cogan 3396 XR 2,773,247 12/1956 Erhardt 339-5 2,892,173 6/1959 Brereton 339-273 XR 3,176,254 3/1965 Fisher et a1. 3395 MARVIN A. CHAMPION, Primary Examiner.

RAYMOND S. STROBEL, Assistant Examiner. 

1. A ROTARY CONDUCTOR FOR TRANSFERRING ELECTRICAL ENERGY INVOLVING HIGH LEVELS OF CURRENT, SAID CONDUCTOR COMPRISING A TUBULAR BODY, CONICAL PINS PROJECTING INTO SAID BODY FROM OPPOSITE ENDS THEREOF IN AXIAL ALIGNMENT WITH EACH OTHER SAID BODY, A SET OF SEGMENTAL BRUSHES ARRANGED CIRCUMFERENTIALLY AROUND EACH CONCIAL PIN, AND MEANS RESISIENTLY URGING SAID BRUSHES INTO ELECTRICAL ENERGY TRANSFERRING CONTACTING RELATION WITH SAID PINS SAID BODY. 